Effects of ulotaront on brain circuits of reward, working memory, and emotion processing in healthy volunteers with high or low schizotypy

Ulotaront, a trace amine-associated receptor 1 (TAAR1) and serotonin 5-HT1A receptor agonist without antagonist activity at dopamine D2 or the serotonin 5-HT2A receptors, has demonstrated efficacy in the treatment of schizophrenia. Here we report the phase 1 translational studies that profiled the effect of ulotaront on brain responses to reward, working memory, and resting state connectivity (RSC) in individuals with low or high schizotypy (LS or HS). Participants were randomized to placebo (n = 32), ulotaront (50 mg; n = 30), or the D2 receptor antagonist amisulpride (400 mg; n = 34) 2 h prior to functional magnetic resonance imaging (fMRI) of blood oxygen level-dependent (BOLD) responses to task performance. Ulotaront increased subjective drowsiness, but reaction times were impaired by less than 10% and did not correlate with BOLD responses. In the Monetary Incentive Delay task (reward processing), ulotaront significantly modulated striatal responses to incentive cues, induced medial orbitofrontal responses, and prevented insula activation seen in HS subjects. In the N-Back working memory task, ulotaront modulated BOLD signals in brain regions associated with cognitive impairment in schizophrenia. Ulotaront did not show antidepressant-like biases in an emotion processing task. HS had significantly reduced connectivity in default, salience, and executive networks compared to LS participants and both drugs reduced this difference. Although performance impairment may have weakened or contributed to the fMRI findings, the profile of ulotaront on BOLD activations elicited by reward, memory, and resting state is compatible with an indirect modulation of dopaminergic function as indicated by preclinical studies. This phase 1 study supported the subsequent clinical proof of concept trial in people with schizophrenia. Clinical trial registration: Registry# and URL: ClinicalTrials.gov NCT01972711, https://clinicaltrials.gov/ct2/show/NCT01972711

 Behavioural performance in the ETB o FERT: % accuracy for each emotion, % misclassifications for each emotion, reaction time for correct answers in each emotion, reaction time for all emotions, target sensitivity for each emotion, response bias for each emotion. o ECAT: % accuracy for each condition, reaction time for each condition. o EREC: number of words recalled for each characteristic, number of commission errors. o FDOT: % accuracy, average reaction time and average vigilance scores for correct answers for each emotion and condition. o EMEM: % accuracy, % false alarms, average reaction time, target sensitivity and response bias for each characteristic.  Change from baseline in BPRS at Visit 2.

Interim analysis
The protocol included an independent interim analysis after approximately 50% recruitment to guide planning for other studies of ulotaront with no bearing on the continuation of the present study.

Task descriptions and analysis N-Back task
Subjects were shown a series of letters and asked to indicate if the letter presented was an "x" (0-Back) or if it matched letters shown in one (1-Back), two (2-Back) and three (3-Back) previous trials with increasing difficulty level. A series of alphabet letters were presented one at a time on a color monitor. Participants were instructed not to respond until they saw the same letter twice following one another. The task had three levels of difficulty according to the number of letters in between the two matching letters. In the 1-back test the two letters followed each other immediately. In the 2-back test the target letters were separated by one letter and in the three back two letters separated the target letters. Thus, participants had to hold in mind one, two, or three letters. Consequently, the 1-back test exerted the lowest load on working memory and the 3-back task the highest. 0-back blocks controlled for attending to the task where participants simply needed to respond when they saw the letter "x." There were 4 blocks of 10 trials for each condition (0, 1, 2, or 3-back) presented in a fixed pseudorandom order.

fMRI analysis
Echo-planar T2*-weighted images were acquired with a Siemens 3T-TIM Trio scanner with body transmit and 12-channel head receive coils (Oxford) ora Philips 3-Tesla Achieva MRI scanner and 8 channel coil (Manchester). Data were generated using a 3 x 3 x 3.5mm voxel resolution; 2000ms repetition time (TR); 28ms inversion/echo time; and 87 o flip angle. Thirty-seven 3mm slices were acquired, descending sequentially parallel to the anterior-posterior commissural line. Data were collected in 315 volumes/2 runs with two 636s dummy scans/run. Field maps were acquired using a dual 2D gradient-echo with echoes at 5.19 and 7.65ms (444ms repetition time). Data were produced using a 64 x 64 x 40 grid with 3mm isotropic voxel resolution. Anatomical reference images were acquired in ascending slice order within 356s using a magnetisation-prepared rapid gradient-echo sequence with 0.78 x 0.8 x 0.78mm voxel resolution on a 208 x 256 x 200 grid, and TE/TI/TR=4.8/1100/2040ms. fMRI data processing Statistical Parametric Mapping (SPM8) was used to analyse fMRI data. Images were corrected for time differences, realigned, normalized and smoothed with an 8mm Gaussain kernel. Artifact Detection Tools (ART) from the NeuroImaging Tools and Resources Collaboratory was used to detect artifacts in time-series data. Motion regressors were used in first level analysis. Participants with more than 15% outlying volumes were excluded. Image data were converted to Neuroimaging Informatics Technology Initiative format and preprocessed using SPM or FMRIB Software Library (FSL) analysis packages. Images were realigned using a least squares approach and 6-parameter rigid body spatial translation. A representative realigned image was used to derive parameters for spatial normalisation to the Montreal Neurological Institute standard template. To discriminate between task/intervention-related effect and noise, signals were fitted to a general linear model and β-values used to construct probability maps to give a parameter-estimate image for each subject and task condition. The outcome was an estimated contrast coefficient β and standard error (% BOLD signal change) from time-series analyses for each voxel. Inputs for primary second level ROI analyses were the weighted mean β per subject, task and ROI. In addition, whole brain inspection with a smallvolume correction (SVC) family-wise error threshold of p<0.05 and correction for 6 ROI was carried out. For the MID task, event-related design was carried out and events of interest were divided into anticipatory and outcome phases/trial. The contrasts win/neutral and loss/neutral were modelled for the anticipatory and outcome phases. The contrast for the N-back was 1,2 and 3 back versus 0-back.
Resting state (RS) fMRI analysis 20 spatially independent components were extracted using independent component analysis (ICA) using the Group ICA of fMRI toolbox (GIFT). Components that spatially correlated with highest r for dorsal (d) and ventral (v) default mode network (DMN) masks from Stanford University were extracted and analyzed further. Component 18 had the highest correlation to the dDMN mask (r=0.56) and component 6 had the highest correlation tovDMN mask (r=0.26; Figure 9.7.6.1). Intensity maps for each component were reconstructed for each individual and the resulting maps entered into a three 3-way (treatment x schizotypy x site) ANOVA for each pair-wise treatment comparison (ulotaront vs. placebo, ulotaront vs. amisulpride and amisulpride vs. placebo).A 3-level analysis was carried out: 1) ROI analysis, in which the mean intensity value per individual was extracted for the entire component/network; 2) small volume correction (SVC) using a mask of the entire network: and 3) whole brain voxel-wise analysis where cluster-wise inference was applied. The same ROI approach was used for the salience and executive networks.  C.